Textiles provide an excellent medium for the growth of microorganisms when the basic requirements such as nutrients, moisture, oxygen, and appropriate temperature are present. The large surface area of textiles also assists in the growth of microorganisms on the fabric. The major problems associated with microorganism growth in textiles are related to hygiene and fabric deterioration. With existing technologies, antimicrobial compounds such as silver, copper, quaternary ammonium compounds are generally applied on the fibers either through coating or are added during melt mixing prior to spinning. The major drawbacks of these fibers are that the antimicrobial compounds release very fast. The amount of antimicrobial agent released during laundering is also high, which affects the durability of the finished fabric. Metals such as silver are generally applied on the fibers in the form of a very thin coating deposited through a sputtering technique, an example of which is the commercial antimicrobial nylon fibre “X-STATIC®”. This thin film coating is prone to crack during processing and use due to the mismatch in extensibility between the fibre and the coating. Apart from this, the strength of the fibre/fabric is also often reduced after the application of a durable antimicrobial coating or finishing.
Thus, there remains a need for a highly durable anti-microbial textile material having enhanced retention of antimicrobial properties upon repeated use and washings without affecting the textile properties such as handle and feel. The controlled release of active agent over a period of time is also a desirable property for certain applications.
The modification of nanoclays with organic compounds and their application as nano-filler finds use in the preparation of hybrid polymer nanocomposite materials due to improved mechanical, thermal, electrical, barrier and optical properties. See Alexandre, M., Dubois, P., Materials Science and Engineering. 28, 2000, pp. 1-63. Organic modified clay is generally prepared through ion exchange of the metal cations in the clay with organophilic cations such as quaternary ammonium salts. It has been reported recently that organoclay containing cationic surfactant or quaternary ammonium salt and long hydrophobic chain show excellent antimicrobial properties. See Nigmatullin, R., Gao, F., Konovalova, V., Journal of Material Science. 43, 2008, 5728. The use of clays such as Montmorillonite, Laopnite, Mingguang Polygorskite, AND Na-clinoptilolite as a support medium or carrier for antimicrobial agents as well as antimicrobial drug has also been reported recently due to their potential use in water treatment, food packaging, and drug delivery material. See Zhou, Y., Xia, M., Ye, Y., Applied Clay Science, 27 (2004) 215; Hu, C-H., Xia, M-S. Applied Clay Science. 31 (2006)180; Magana, S. M., Quintana, P., Aguilar, D. H., Toledo, J. A., Angeles-Chavez, C., Cortes, M. A., Leon, L., Freile-Pelegrm, Y., Lopez, T., Torres Sanchez e, R. M., Journal of Molecular Catalysis A: Chemical. 281 (2008)192; Malachová, K., Praus, P., Pavlí{hacek over (c)}ková, Z., Turicová, M., Applied Clay Science. 43 (2009) 364; Aihara, N., Torigoe, K., Esumi, K., Langmuir. 14 (1998) 4945; Zhao, D., Zhou, J., Liu, N., Applied Clay Science 33 (2006) 161; and Top, A., Úlkú, S. Applied Clay Science, 27 (2004).
The antimicrobial agents such as silver, copper, quaternary ammonium compounds, cationic drugs and like have been intercalated and absorbed on clay surfaces through an ion exchange mechanism. These incorporated antimicrobial/active ions/drugs subsequently release from the clay surface in a controlled manner and show excellent antimicrobial activity against pathogenic bacteria.
Montmorillonite (MMT) is classified as 2:1 phyllosilicate clay. It has a unit crystal lattice formed by one alumina octahedral sheet sandwiched between two silica tetrahedral sheets and the interlayer between units contain positive cations such as Na+, K+, Ca++ etc. and water molecules. Due to this crystalline arrangement, montmorillonite is able to expand and contract the interlayer while maintaining two dimensional crystallographic integrity and is characterized by octahedral and/or tetrahedral substitution and high ion exchange capacities (70-120 mequiv/100 g). Magana et al., have studied the antimicrobial activity of the montmorillonite clay modified with silver and found that the antimicrobial activity or silver loading on the clay is dependent on the cation exchange capacity of the clay and the availability of ionic silver to be in contact with the bacteria. The cation exchange capacity of the clay can be modified via thermal, mechanical or chemical treatments. See Top et al. Hu and Xia have studied three different kinds of montmorillonite such as calcium montmorillonite, sodium montmorillonite and acid activated montmorillonite and their ion exchange with Cu++. See Hu et al. The Cu++ modified clays shows very good antimicrobial activity. Menga et al., have studied chlorhexidine acetate (CA)/montmorillonite intercalation composites and its antimicrobial potential with pathogenic bacteria, Staphylococcus aureus and Pseudomonas aeruginosa. See Menga, Na., Zhoua, N-L., Zhang, S-Q., Shena, J. International Journal of Pharmaceutics, 382 (2009).
The application of quaternary ammonium ion based antimicrobial clay into a polymer matrix in the form of films has been explored recently. The introduction of commercially available organo-clays such as Closite 30B and Closite 10A into Nylon 6, Chitosan and PLA matrix significantly suppresses biofilm formation on film surfaces exposed to the bacterial suspension. See Nigmatullin et al.; Wang, X., Du, Y., Yang, J., Wang, X., Shi, X., Hu, Y., Polymer, 47 (2006) 6738; and Rhim, J. W., Hong, S. I., Ha, C. S., LWT Food Science and Technology, 42 (2009) 612. However, there is no literature available on the application of antimicrobial clay based on metal ions in polymer nanocomposite and more specifically for making antimicrobial fibers.